1. Field of the Invention
The present invention relates to a wireless terminal device that is accommodated via a wireless transmission medium and is used to receive desired communication services. The present invention is also concerned with a node device that performs a communication control necessary for providing communication services.
2. Description of the Related Art
Recently, there has been considerable activity in cost reduction of information terminals such as personal computers as the performance thereof has been improved. In many offices, many people use information terminals so that many works are performed efficiently.
In many offices furnished with many information terminals, a LAN (Local Area Network) is introduced in order to integrally manage information and share peripheral devices. Further, a wireless LAN is placed in practice in order to achieve frequent change and flexibility of layout.
FIG. 1 shows an example of a communication system made up of an access network corresponding to a wireless LAN, and a core network connected thereto. An access network 130 and a core network 150 are mutually connected via a communication link 170.
The access network 130 includes a number N of base station devices 131-1–131-M, a base station control device 133, a wireless terminal device 134, and a personal computer (PC) 135. The base station devices 131-1–131-M are connected to the base station control device 133 via given communication links 132. The wireless terminal device 134 is located in any of wireless zones respectively formed by the base station devices 131-1–131-M. The personal computer 135 is connected to the wireless terminal device 134.
The base station control device 133 is made up of a base station interface (hereinafter simply referred to as BSI) unit 136, a core network interface (hereinafter simply referred to as CNI) unit 137, and a controller 138 connected to control terminals of the BSI unit 136 and the CNI unit 137. The BSI unit 136 is connected to ends of the communication links 132. The CNI unit 137 is connected between the BSI unit 136 and one end of the communication link 170.
The wireless terminal device 134 is made up of a terminal interface unit 139, an antenna 140, and a wireless interface unit 141, and a controller 142. The terminal interface unit 139 is connected to the personal computer 135. The wireless interface unit 141 is connected between a power supply terminal of the antenna 140 and the terminal interface unit 139. The controller 142 is connected to control terminals of the terminal interface unit 139 and the wireless interface unit 141.
The core network 150 is made up of a node device 151, one or a plurality of node devices 153-1–153-N, a home location register (hereinafter simply referred to as HLR) 154, and a default forwarder (hereinafter simply referred to as DF) 155. The node device 151 is connected to the other end of the communication link 170. The node devices 153-1–153-N are provided in a ring-shaped transmission network 152.
A personal computer 156 is connected to the node device 153-N.
The node device 151 is made up of an access network interface (hereinafter referred to as ANI) unit 157, a transmission network interface (hereinafter referred to as TNI) unit 158, and a controller 159. The ANI interface 157 is connected to the other end of the communication link 170. The TNI interface 158 is connected to a preceding transmission section of the transmission network 152 and a following transmission section thereof. The controller 159 is connected to control terminals of the ANI unit 157 and the TNI unit 158.
Each of the structures of the node devices 153-1–153-N is the same as that of the node device 151.
In the following description it is assumed that the wireless terminal device 134 is a wireless LAN interface card attached to a PCMCIA slot of the personal computer 135 for the sake of simplicity.
The terminal interface unit 139 of the wireless terminal device 134 receives a call request issued by the personal computer 135, and sends it to the controller 142. The controller 142 determines, at step (1) of FIG. 2, whether the call request is a regular request which includes identification information on the personal computer 135 that issues the call request, a telephone number of an access point to be accessed, an address of a desired site, and so on.
When the answer of step (1) is YES, the controller 142 sends the information included in the call request to the wireless interface unit 141, so that the wireless interface unit 141 is initiated (step (2)).
At step (3), the controller 142 and the wireless interface unit 141 interact with one of the base station devices 131-1–131-M which forms a wireless zone in which the wireless terminal device 134 of interest is located in order to set a channel. It is now assumed that the base station device 131-1 is involved in the wireless terminal device 134 of interest.
The base station device 131-1 performs channel setting under the control of the base station control device 133 connected thereto via the corresponding communication link 132. The base station control device 133 interacts with the node device 151 which faces the base station control device 133 via the communication link 170 in accordance with the sequence of channel setting. Thereby, a call setup arising from the call request is performed in parallel at step (1) of FIG. 3. The above channel setting is performed in order to form a logical channel to be supplied for transmission of a communication signal in a wireless section which will be described later.
In the process of the above-mentioned channel setting and call setting, the controller 138 provided in the base station control device 133 absorbs, via the BSI unit 136 and the CNI unit 137, the difference in the signal formation between the wireless transmission channel formed by the base station device 131-1 and the communication link 170.
In the wireless terminal device 134, the controller 142 acknowledges that a wireless channel has been assigned to its own station when the channel setting is duly performed. Then, the controller 142 forms a path between the antenna 140 and the personal computer 135 via the wireless interface unit 141 and the terminal interface unit 139 at step (4) shown in FIG. 2.
In the above state, a two-way communication path is formed in the transmission section (hereinafter simply referred to as wireless section) extending to the base station control device 133 via the wireless interface unit 141, the wireless transmission path, the base station device 131-1 and the communication link 132.
The base station control device 133 (controller 138), and the node devices 151, 153-1 through 153-N (controller 159 and 159-1–159-N), the HLR 154 and the DF 155 act as a router which performs routing of packets supplied via the communication link 170.
In the wireless terminal device 134, the controller 142 communicates with the base station control device 133 with the following messages based on TCP/IP after the sequence of channel setting is duly completed. Thereby a connection is established.
The controller 142 creates a registration request, which includes the dial number, identification information, and authentication number of the wireless terminal device 134 of interest (step (5) shown in FIG. 2 and step (1) shown in FIG. 5).
In the base station control device 133, the controller 138 acknowledges the registration request, and then sends, as a packet, via the communication link 170 a terminal information request related to a mobile station and comprised of the dial number, identification information and authentication number included in the registration request (step (2) shown in FIG. 3 and step (2) shown in FIG. 5).
When the HLR 154 is supplied with the terminal information request in the above-mentioned routing, it obtains terminal information applied to a database beforehand and related to the dial number included in the above terminal information request. The terminal information thus obtained is sent to the transmission path 152 as a packet (step (1) of FIG. 4 and step (3) of FIG. 5).
In the base station control device 133, when the controller 138 is supplied with the terminal information in the routing, it interacts with the controller 142 of the wireless terminal device 134 so that control information pertaining to the terminal information is transferred between the HLR 154 and the controller 142. Thereby, the setting of a secret-speech key to be applied to the wireless transmission path is performed in addition to the authentication (step (6) of FIG. 2, step (3) of FIG. 3, and steps (4) and (5) of FIG. 5).
Further, when the authentication and setting of the secret-speech key are completed, the controller 138 creates a registration request including the identification information on the corresponding wireless terminal device, and sends it to the communication link 170 as a packet (step (4) of FIG. 3 and step (6) of FIG. 5).
The HLR 154 is supplied with the above registration request. Then, given information included in the registration request the contents thereof are registered in the database (step (2) of FIG. 3). Thus, the mobile station having the established connection for communications is identified (step (3) of FIG. 3). Then, a registration acknowledgement indicating the above is sent to the transmission path 152 as a packet (step (4) of FIG. 4, and step (7) of FIG. 5).
The above registration acknowledgement is transmitted to the base station control device 133 in the aforementioned routing. The controller 138 of the base station control device 133 gives the registration acknowledgement to the wireless terminal device 134 via the wireless section (step (5) of FIG. 3, and step (8) of FIG. 5).
In the wireless terminal device 134, the controller 142 acquires the registration acknowledgement via the wireless interface unit 141, and recognizes it. Then, the controller 142 forms, between the personal computer 135 and the wireless transmission path (antenna 140), a path passing through the terminal interface unit 139 and the wireless interface unit 141 (step 7) of FIG. 2. Further, the controller 142 supplies a message indicating the above (hereinafter referred to as a connection establishment message) to the personal computer 135 via the terminal interface unit 139 (step (8) of FIG. 2, and step (9) of FIG. 5).
The personal computer 135 recognizes the connection acknowledgement message, and communicates with the wireless terminal device 134 while sending and receiving desired transmission information in the formation of a train of IP packets.
As described before, the main processes among the series of processes carried out by the interaction of the wireless terminal device 134, the base station device 131-1, the base station control device 133, the node device 151 and the HLR 154 will be referred to as connection process as shown in FIGS. 2 through 4.
In the process of transmission and reception of transmission information carried out based on the TCP/IP, as shown in FIG. 6, the IP layer and the TCP layer are not terminated at any of the base station device 131-1, the base station control device 133 and the node device 151. That is, the base station device 131-1, the base station control device 133 and the node device 151 merely present a link at a layer lower than the IP layer.
In the above-mentioned related art, the wireless terminal device 134 cannot receive connection-oriented communication services unless the above-mentioned connection process is performed by the interaction of the base station device 131-1, the base station control device 133, the node device 151 and the HLR 154, and the wireless channel allotted under the channel setting performed by the base station controller 138 in the connection process continues to be captured.
However, the above scheme needs a larger scale of hardware incurring higher cost as the number of wireless terminal devices which concurrently receive connection-oriented communication services increases. Even if the scheme can be implemented from technical viewpoints, it is not of practical use because the wireless channels are limited resources.
Particularly, in a case where the care network 150 corresponds to the Internet or accommodates access points providing access to the Internet, it is strongly desired to provide communication services as those of a connectionless network without destroying the arrangement in which wireless terminal devices are accommodated via the wireless communication paths.